Two fluid drilling system



Sept. 6, 1960 J.'M. CAMP ET AL 2,951,680

TWO FLUID DRILLING SYSTEM Filed Nov. 5, 1956 2 Sheets-Sheet 1 FIG-3 7/ \r 40 By Attorney P 1960 J. M. CAMP ETAL TWO FLUID DRILLING SYSTEM 2 Sheets-Sheet 2 RILL LLAR D CO SEAL FIG-IO Filed Nov. 5, 1956 FIG.'7

John M. Camp John E Ecke! Max C. Sons B w,0 7W Attorney 2,951,680 TWO FLUID DRILLING SYSTEM John M. Camp, John E. Eckel, and Max C. Sons, Tulsa,

Okla, assignors, by mesne assignments, to Jersey Production Research Company Filed Nov. 5, 1956, Ser. No. 620,348

9 Claims. (Cl. 255-43) The present invention is concerned with "the drilling of boreholes in the earth and is more particularly concerned 'with an improved method and apparatus for the drilling of boreholes using a gaseous or gas-containing drilling fluid in conjunction with a heavier drilling mud. The invention provides two separate circulatory systems within the borehole, thereby permitting separate circulation of the drilling fluid to and from the cutting area while a more dense drilling mud is circulated in the annulus of the borehole.

It has long been recognized that the relatively high density of the drilling muds used in conventional rotary drilling systems has an adverse effect upon the cutting action of the drill bit and that improved drilling rates could be obtained by reducing the hydrostatic head upon the formation. The use of a gas or a drilling mud whose density has been decreased by the addition of gas in place of the conventional drilling mud has therefore been suggested. Because of the numerous functions which must be performed by the drilling mud in conventional systems, however, this has proved impractical in many instances. In conventional rotary drilling, the drilling mud acts as a plastering or sealing agent to protect and maintain the borehole walls, as a lubricant, as a heat transfer medium, and as a carrier medium for removing ,cuttings from the borehole. The hydrostatic head of the drilling mud also serves to prevent high pressure gas'or oil formations from blowing out of control. The caving of the borehole walls and the entry of water into the borehole from the surrounding strata pose particularly severe problems where a gas or gas-containing liquid is used in place of the conventional mud. The presence of Water when a gas is used as the drilling fluid causes the cuttings from the drill bit to agglomerate intoa gummy mass which adheres to the bit, the borehole Walls and the drill stem. This leads to decreased drilling rates and may in time completely clog the drilling apparatus,

necessitating shut-down to permit cleaning out of the borehole. If the flow of water is great ,enough, normallyavailable air pressures and volumes may not be suflicient to lift an accumulated column of water from the borehole. In such cases drilling with air or gas must be abandoned and conventional mud drilling at a reduced formations will be encountered.

-It is therefore an objective of the present invention :to provide an improved method of drilling boreholes wherein two separate circulatory systems are maintained within the borehole, permitting the use of air ora gas as a United States Patent-O 2,951,680 Patented Sept. 6, 1960 drilling fluid and the use of a heavier, more dense fluid as a means for sealing the borehole walls and preventing caving.

A further objective of the invention is to provide a means for drilling under a low hydrostatic pressure at the bottom of a borehole while maintaining in the remainder of the borehole a much higher hydrostatic pressure, thus providing control of high pressure strata surrounding the borehole.

Other objectives will be apparent from the description of the invention, the accompanying drawings, and the appended claims.

To accomplish these objectives, the drilling apparatus of this invention comprises a rotary drill bit, a drill collar having multiple conduits therein for the passage of fluids and fitted with a moveable packer which forms a tight closure between the outer surface of the drill collar and the walls of the borehole, and a drill pipe having multiple conduits corresponding to those of the drill collar. The drill pipe and collar are connected by box and pin joints which permit the making up of joints without the necessity of orienting and aligning the internal conduits. In drilling with the apparatus of the invention, a heavy, dense drilling mud is circulated in the annulus of the borehole to maintain and seal the borehole walls; while a gas or gas-containing liquid is circulated to and from the drill bit to perform the other functions conventionally performed by the drilling mud. The reduced hydrostatic head on the formation permits improved drilling rates while many of the difiiculties normally encountered in air or gas drilling are avoided. It is thus seen that the ingress of water from upper formations into the borehole and thence down the borehole to the bit is eliminated.

The nature of the invention can perhaps be best understood by referring to the accompanying drawings, in which:

Figure 1 depicts in vertical section taken alongthe line E-E of Figure 2 a drilling apparatus embodying the present invention; I

Figure 2 is a cross-sectional view of the drill collar taken along the line AA of Figure 1;

Figure 3 is a cross-sectional view of the drill collar taken along the line BB of Figure 1;

Figure 4 is a cross-sectional view of the drill collar taken along the line C-Ctof Figure 1;

Figure 5 shows an alternate cross-sectional configuration which may be used for the drill collar and drill p p Figure 6 shows another cross-sectional configuration which may be used for the drill collar and drill pipe;

Figure 7 shows an enlarged sectional view of theqbox of-the drill collar;

Figure 8 shows a cross-sectional view of the drill collar taken along the line D -D of Figure 7;

Figure 9 shows an enlarged sectional view of the pin of the drill pipe; and,

Figure 10 shows a sectional view of the box of Figure 7 and the pin of Figure 9 threaded together to forrna box .and pin joint and rotated counterclockwise fromthe views shown in Figures 7 and 9.

Referring now to Figure 1, the drilling apparatus of the invention comprises a rotary bit 1 attached to a drill collar 2 which is in turn attached to a string of drill pipe 3 extending to the surface of the earth. Rotary .bit=1 may be of any conventional type, including the fishtai-l, disc, roller and cone types. It may employ replaceable blades or cutters. The bit is threaded into drill collar 2 and contains a central passage 4 for the passage of drilling fluid from the drill collar to the cutting surfaces of the bit. v

"drill pipe.

' of the rod within this slot. -19 upward against rod 27 results in the opening of valve and is of the same length as a conventional section of The drill collar contains separate internal conduits 7, 8 and 9, which maybe seen in cross-section in Figures 2 and 3. It will be appreciated that these internal conduits may have other cross sections in lieu of that shown in Figure 2, such as those shownin Figures 5 and 6. I Conduit 7 extends from the box and pin joint 5 'at the upper end of the drill collar to a point below recessed section 6 and fluidly communicates with the an- :nular space between the drill collar and the bore wall below recess 6 through port 11. Conduit 8 extends from the box and pin joint 5 at the upper end of the drill collar to a point below recessed section 6 and fluidly communicate s with the annular space between the drill collar and the bore wall 10 above recess 6 through port 12.

Conduit 9 extends from the box and pin joint 5 at the upper end of the drill collar to the, lower end thereof and communicates with the bore of rotary bit 1. The lower section of conduit 9 forms valve seat 13 and valve 14 is positioned therein below the seat. The valve is spring loaded byspring 15 supported by spider 16, which also serves as a guide for the stern of the valve. The valve is normally in a closed position and is open downwardly 'by pressure exerted by drilling fluid pumped downward through conduit 9. Connected to the upper stem of valve 14 is a sleeve valve 17 which extends through opening 18 between conduits 7 and 9 and slides vertically in the 'two conduits, The sleeve valve is normally closed, closing port 11 between conduit 7 and the annular space surrounding the drill collar.

As valve 14 opens sleeve valve 17 also opens, admitting fluid into conduit 7 from the annular space.

Positioned upon drill collar 2 within recessed section 6 is anannular sleeve 19 which is provided with a plurality of closely spaced ports 20 extending through the sleeve. Sleeve 19 is free to turn and slide about the drill collarwithin the confines of the recessed section and seal rings 21 maintain a seal between the sleeve and the surface of the drill collar. The seal rings may be made of rubber, plastic, leather or similar materialand are retained in grooves in the inner surface of the sleeve above and below the port 20. The ring may have any conventional configuration, such as the ,O or chevron configurations. Affixed to the outer surface of the sleeve and carried thereon is an inflatable packer 22 which is preferably made of rubber, although various plastics, canvas or other fabrics may be used. Steel wire or other cord may be incorporated into the packer fabric to lend added strength and rigidity. The packer must possess suflicient elasticity to form a tight seal against the bore wall when inflated, even though the wall surface may be somewhat irregular because of caving and washouts.

The wall of the drill collar 2 contains a port 23 located near the upper end of recessed section 6 which together with port 20'establishes fluid communication between the interior of packer 22 and conduit 8 when the packer is in its uppermost position as more fully shown hereinafter. This port is normally closed by a slideable valve 24 which is shaped to fit the curved inner wall of conduit '8. Valve 24 is held in a normally closed position over the port by a helical spring 25 supported by shoulder 26 which protrudes from the inner wall of conduit 8. 'A rod 27,

shown more clearly in Figure 3, extends from the outer surface of valve 24 through a slot 28 in the drill collar wall and movement ofthe valve is limited by movement Relative movement of sleeve 24 and the vertical alignment of port 20 in the sleeve with port 23 in the drill collar. Port 20 extends radially through the wall of sleeve 19. A port 29 similar to port 23 is located near the bottom of the recessed section and together with port 20 establishes fluid communication be tween the interior of packer 22 and conduit 8 when the packer is in its lowermostposition in relation to recess 6, as will more fully be shown hereinafter. This port is normally closed by a slideable valve 30 positioned within the conduit by a spring 31 supported by shoulder 32. Rod 33 attached to the valve extends through slot 34 and movement of the valve is limited thereby. Relative movement of sleeve 19 downward against rod '33 results in the opening of valve 30 and the alignment of port 20 in the vertical sleeve with port 29 in the drill collar.

Drill collar 2 is connected to drill pipe 3 by means of box and pin joint 5, which is shown in greater detail in Figures 7 through 10. The box and pin joint consists of an internally threaded box incorporated in drill collar '2 and an externally threaded pin incorporated in drill pipe 3. At the joint the internal conduits of the drill collar and drill pipe openinto concentric passages such that no alignment of the conduits is necessary when making up the joint. Thus in Figure 7, which depicts the box of drill collar 2, internal conduits 7, 8 and 9 fluidly connect with concentric fluid chambers 35, 36 and 37. These are shown more clearly in Figure 8. 7

Referring now to Figure 9, the pin of drill pipe 3 similarly contains three concentric fluid chambers 38, 39 and 40 corresponding to' chambers 35, 36 and 37 in the drill collar. 'Chamber 38 fluidly connects with internal conduit 41 in the drill pipe, chamber 39 fluidly connects with conduit 42, and chamber 40 fluidly connects with conduit 43. Conduits 41, 42 and 43 in the drill pipe correspond to conduits 7, 8 and 9 in the drill collar. The portion of the pin bounding chambers 39 and'40 essentially forms two concentric tubular walls, 44 and 45. Each of these tubular walls has a seal ring 46 set in a groove in its outer surface. These seal rings are preferably made of rubber but may be made of plastic, leather or other common sealing materials and may be of the chevron or of any other common type instead of the O-n'ng type illustrated. g

When the box of drill collar 2 and the pm of drill pipe 3 are made upto form a joint, as shown in Figure 10 which has been rotated 90 counterclockwise from the view as shown in Fig. 9, tubular walls 44 and 45 extend intochambers 36 and 37 and seal rings 46 form a tight through chambers 40 and 37 into conduit 9 of the drill collar 2 without escaping into adjacent chambers or conduits. Since the fluid chambersat the joint are separated concentrically, rather than radially as in the drill collar and drill pipe, there is no need for alignment of the conduits in the pipe and collar when the joint is made up. Any desired 'pipe dope or sealing compound may be applied to the threads of the joint to prevent galling. Many commercial compounds are available and well known in the art," v i The drill pipe 3 used in the invention contains three internal conduits similar in cross section to those of the drill collar 2. As pointed out heretofore, these conduits may be arranged as shown in Figure 2 or alternately may have one ofthe cross sections shown in Figures 5 and 6. Drill pipe tube 2, is shown as having channels 52, 54, and 56. In Fig. 6 drill pipe 2 is shown as having channels 58, 60, and 62. Each length of drill pipe has a pin at one end and a' box at the other and joints similar to that described between the drill collar and the drill pipe are used between adjacent lengthsof drillpipe.

- The drill pipe is made in standard lengths.

In drilling in accordance with'the' present invention,

referring again'to' Figure: 1, a drilling mudisp'urnped downward through the drill pipe 3 and into conduit 8 .of drill collar 2. Sleeve 19 is at the bottom of recessed section 6, as will be apparent later, andbears upon rod 33 extending through slot 34. The weight of the sleeve upon the rod holds valve 30 below port 29 and compresses spring 31. Port 20 in the sleeve is thus vertically aligned with port 29 in the drill collar. Valve 24 is held in position over port 23 by spring 25. The downflowing drilling mud reaches the bottom of conduit 8 and flows through port 29 in the drill collar wall and through port 20 in the sleeve, inflating the packer 22 and expanding it against the borehole wall. The mud continues to flow in conduit 8, leaving the conduit through port 12 above the packer and filling the annular space between the borehole wall 10 and the drill string above the packer. The packer prevents the mud from entering the area surrounding the bit. The borehole wall above the packer is thus strengthened against caving and sealed against the entry of water and gas from the surrounding formations. The mud also serves as a lubricant between the borehole wall and the drill collar and drill pipe above the packer. Although any conventional drilling mud may be used with the apparatus, it will be understood that many of the special propertiw of drilling muds used in conventional rotary drilling operations will be unnecessary because the mud is not used in the cutting area surrounding the drill bit. A conventional suspension of clay in water may be used and the density and viscosity are limited primarily by the requirement that the mud be easily pumpable through the drill pipe and drill collar 'oints.

J Rotation of the drill string from the surface by means of conventional rotary drilling equipment is commenced and air, gas, or a drilling mud whose density has been decreased by the incorporation therewith of air or gas is pumped downward through the drill pipe and into drill collar conduit 9. This drilling fluid travels the length of the drill collar, passes through opening 4 in the stern of rotary bit 1, and is introduced into the cutting area surrounding the bit. As the cutters of the bit rotate against the formation at the bottom of the borehole, cuttings are produced and these are picked up by the stream of drilling fluid introduced at the center of the bit and carried upward into the annular space below the packer. The cutting-laden fluid then enters drill collar conduit 7 through port 11 and is conducted through the drill pipe to the earths surface.

As drilling continues and rotary bit 1 cuts into the formation, the weight ,of the drill collar 2 and drill pipe 3 forces the drill stem to move downward. Sleeve 19 and packer 20 do not move but instead are held in position by the force of the packer against the borehole wall, the drill collar sliding through the sleeve. As the collar continues to move downward, spring 31 expands and forces valve 30 upward until rod 33 contacts the upper edge of slot 34, at which point port 29 is covered by the valve. This prevents the escape of drilling mud into the area below the packer through the port, which is no longer covered by sleeve 19. The packer itself is sealed off as the collar moves through the sleeve and therefore remains inflated.

As the drill collar continues to move downward through sleeve 19, rod 27 comes into contact with the upper edge of the sleeve 19. The downward movement of valve 24 is thus halted and spring 25 is compressed as the drill collar continues to move down. When rod 27 is in its uppermost position in slot 28, port 23 is open and fluidly communicates with the interior of the packer through ports 20 in the sleeve. At this point the apparatus has drilled down the length of a section of drill pipe and the pumps on the surface are stopped to permit the addition of another section of pipe to the upper end of the drill string. The multiple conduit drill pipe used in accordance with the invention is made in standard pipe lengths to permit its use with conventional derricks,

racks and the like. Pressure on the inside of the packer is released by stopping the pumps and the packer deflates,

the sleeve and packer dropping to the bot-tom of the recessed section of the drill collar in the position shown in Figure 1. The weight of the sleeve 19 and packer 22 overcomes the friction of seals 21. Valve 24 is closed by spring 25 and valve 30 is opened by the weight of the sleeve and packer on rod 33. At the same time drilling mud from the annular space above the packer drops down into the bottom of the borehole around the bit, increasing the pressure in this area. The differential pressure thus exerted on valve 14 forces the valve upward against the valve seat 13, closing conduit 9 and preventing the entry of drilling mud into the conduit. Sleeve valve 17, interconnected with valve14, is also closed, preventing mud from entering conduit 7.

The mud pumps are started again when a new section of drill pipe has been added to the drill string and mud pressure is again built up in conduit 8. As shown in Figure 1, when the sleeve is in its lowermost position against rod 33 in slot 34, valve 30 is held in a downward position against the force of spring 31 and thus port 29 again communicates with the interior of the packer through port 20 in the sleeve. The packer is reinflated with drilling mud, again sealing off the bottom of the borehole. The air, gas or gas-containing drilling fluid is then pumped downward through conduit 9, building up pressure and opening valves 14 and 17. The drilling mud in the annular space below the inflated packer is carried upward by the drilling fluid through port 11 into conduit 7, through which it is conducted into the drill pipe and thence to the surface. Rotation of the drill string is started again and drilling continues.

From the foregoing it can be seen that the apparatus of the present invention permits drilling under a substantially decreased hydrostatic head while a conventional high density drilling mud is maintained in the borehole in order to prevent caving of the walls and entry of formation fluids. Substantially improved drilling rates can thus be obtained in locations where conventional air or gas drilling in unfeasible. The use of an inflatable packer which can be deflated and lowered in the borehole as the drill string advances permits effective separation of the drilling mud and the lighter drilling fluid and prevents undue wear and abrasion of the packer surface. Air, nitrogen, methane, carbon dioxide and similar gases may be used as the drilling fluid or may be incorporated into a drilling mud to significantly lower its density and thu reduce the hydrostatic head on the drill bit.

It Will be obvious to those skilled in the art that numerous modifications may be made in the apparatus described without departing from the spirit of the present invention and it is intended that the invention be limited only by the scope of the following claims.

The invention having thus been described and illustrated, what is claimed is:

1. Apparatus for drilling boreholes in the earth comprising in combination a string of multiple conduit drill pipe; a drill collar connected to said drill pipe having an intermediate section defined by upper and lower limits and of a character to carry a borehole packer, said drill collar containing multiple internal conduits respectively communicating with the conduits in said drill pipe, a first of said conduits in said drill collar extending through said drill collar, a second of said conduits in said drill collar having an external port below said intermediate section, a third of said conduits in said drill collar having an external port above said intermediate section and upper and lower external port within said intermediate section; an inflatable borehole packer vertically slideable within the limits of said intermediate section and rotatable with respect to said drill collar, said packer having an inflating port on the inner wall thereof; lower valve means insaid third conduit; upwardly biasing means for holding said lower valve means in a closed position over said lower port within said intermediate section; means connected to of said borehole packer thereon whereby said lower port is open when said borehole packer is in its lowermost position within said intermediate section and fluid communication is established between said third conduit and the interior of said packer; upper valve means in said third conduit; downwardly biasing means for holding said upper valve means in a closed position over said upper port within said intermediate section; means connected to said upper valve means responsive to upward pressure of said borehole packer thereon whereby said upper port is open when said borehole packer is in its uppermost position within said intermediate section and fluid com- .munication is established between said third conduit and the interior of said packer; and a drill bit connected to said drill collar containing a central passage therethrough fluidly communicating with said first conduit in said drill collar.

2. Apparatus for drilling boreholes in the earth comprising in combination a string of multiple conduit drill pipe; a drill collar connected to said drill pipe having an intermediate section of decreased outer diameter and containing internal conduits respectively communicating with the conduits of said drill pipe, a first of said conduits in said drill collar extending through said drill collar and having an outlet at the bottom thereof, a second ofsaid conduits in said drill collar extending to a port in the side of said drill collar below said intermediate section, a third of said conduits in said drill collar extending to a lower port in the side of said drill collar within said intermediate section and communicating with an upper port in the side of said drill collar within said intermediate section and with a port in the side of said drill collar above said intermediate section; an inflatable borehole packer vertically slideable within said intermediate section and rotatable with respect to said drill collar, said packer having an opertured annular sleeve; valve means in said drill collar for opening said first and second conduits responsive to the application of pressure in said first con- .duit of a greater magnitude than the pressure in the borehole; lower valve means in said third conduit normally biased to close said lower port in said intermediate section; a rod member connected to said lower valve means and responsive to downward pressure from said packer so that .said lower port in said intermediate section is open and fluid communication is established between said third conduit and the interior of said packer when packer is in its lowermost position in said intermediate section and said lower port is closed when said packer is moved upwardly in said intermediate section; upper valve means in said third conduit normally biased to close said upper port in said intermediate section; a rod member connected to said upper valve means and responsive to upward pressure from said packer so that said upper port in said intermediate section is open and fluid communication is established between said third conduit and the interior of said packer when said packer is in its uppermost position in said intermediate section and said upper port is closed when said packer is moved downwardly in said intermediate section; and a drill bit connected to said drill collar having a central passage therethrough fluidly communicating with said first conduit.

3. Apparatus as defined by claim 2 wherein said drill ,pipe and drill collar are connected by box and pin joints .in which individual conduits of said pipe separately communicate with individual conduits of said collar through pipe; a drill collar connected to said pipe having an intermediate section of reduced outer diameter upon which a borehole packer may be mounted and having multiple internal conduits respectively communicating with the conduits of said drill pipe, a first of said conduits in said drill collar extending through said drill collar, a second of said conduits insaid drill collar extending to and conimunicating withaport in the side of said drill collar below said intermediate section, a third of said conduits extending to and communicating with a lower port in the side of said drill collar within said intermediate section and communicating with an upper port in the side of said dril-l collar within said'intermediate section and with a port in the side of said drill collar above said intermediate section; an inflatable borehole packer vertically slideable within said intermediate. section and rotatable with respect to said drill collar, said packer comprising a sleeve containing a plurality of ports extending therethrough and a packer fabric mounted on the exterior of said sleeve and inflatable through said ports in said sleeve;

valve means for opening said first conduit and said port in said collar communicating with said second conduit in response to the application of pressure in said first conduit; a lower slidable valve in said third conduit normally biased to close said lower port in said intermediate section; a rod member connected to said lower valve and extending externally of said intermediate section, said rod member being responsive to downward pressure from said packer sleeve to open said lower valve and establish communication between said third conduit and said packer through said ports in said packer sleeve when said packer is in its lowermost position in said intermediate section and to permit said lower valve to close when said packer moves upwardly within said intermediate section; an upper slidable valve in said third conduit normally biased to close said upper port in said intermediate section; a rod member connected to said upper valve and extending externally of said intermediate section, said rod member being-responsive'to upward pressure from said packer sleeve to open said upper valve and establish communication between said third conduit and said packer through said ports in said packer sleeve when said packer is in its uppermost position in said intermediate section and to permit said upper valve to close when said packer moves downwardlywithin said intermediate section; and a drill bit connected to said drill collar having an axial passage therethrough fluidly communicating with said first conduit in said drill collar.

6. A method for drilling a borehole in the earth utilizing a gaseous drilling fluid while maintaining a high density fluid in the borehole annulus which comprises closing the annular space between a drill string and the wall of said borehole at a point near the lower end of said drill string; injecting said drilling fluid to the bottom of said borehole under suflicient pressure to return said drilling fluid upwardly to the surface; and injecting in the borehole annulus said high density fluid at a point adjacent to and above the point at which said annular space between said drill string and the wall of said borehole is closed. a

7. A method as defined by claim 6 wherein said drilling fluid is air.

8. A method as defined by claim 6 wherein said high density fluid is drilling mud.

9. The improvement defined by claim 6 wherein said upper zone is moved downwardly at intervals as said borehole is advanced;

References Cited'in the file of this patent UNITED STATES PATENTS 

